I've taken great care to make sure my power cables do not occupy the same space or touch or cross my other cables but the remainder of my cables run parallel as needed.
All are above the floor/not in wall and are exposed.
Should I be concerned about coax/speaker cable/sub cable/ cat5 cables crossing, touching etc?
The only noise/hum in my system comes from the PVR. Its about to be replaced.

basically, i think power cables can all be run together, even tied together, but signal cables should be at least a few inches away from power cables and run parallel for as short a distance as possible.

touching is ok and crossing is very good.

Coax/sub cables are shielded so you really don't have to worry about with them. Cat 5 with twisted pairs is generally ok as well

Any time a power cable needs to come near a signal cable, they should be run as perpendicular as possible to make the point that they touch as small as possible.

None of my power cables physically touch the remaining cabling.
Most of my speakers cables, Coax, cat5 cables run in a group around the room as required. They touch several times in several locations.
I've cut each cable long enough to run them through the floor and up walls once I've decided on the locations. There is a loop of cable in the front corners.

Just some notes:
Coax is shielded to prevent interference.
CAT5 can be shielded and is inheritly protected from outside signal noise due to its twists. Although, must of that "noise" comes from other pairs in the same CAT5 cable, thus each pair is twisted differently inside the CAT5 cable itself.

Speaker signal wire is potentially your most "powerful" set of wires running in your bundle. You won't see much interference coming into the speaker signal from the other two sources, and those other sources are designed to block signals from leaking in/out.

Long story short, you are fine unless doing really long cable/wire runs.

Now, just remember, a coil of copper wire with electricity running through it is an electro-magnet. Not a strong enough one to worry about though. Just sayin'...